There was no indication that crew performance played a role in this accident or that either aeroplane was ill-equipped as to conspicuity devices or that those devices were not used appropriately. A realistic probability of either aeroplane detecting the other was 25percent, and without detection, the collision was unavoidable. The two aeroplanes were on a constant collision course; therefore, there was no relative angular movement that could be detected by peripheral vision to aid in detection. There was no other means of alerting either aeroplane as to the presence of the other. ATC does not provide traffic advisories in that airspace and TIS, which is capable of providing specific alerts and was carried by C-GCHN, depends on a ground radar service that is not available in Canada. The failure of the see-and-avoid principle to avert this collision reflects the residual risk that is inherent in sole reliance on unalerted see-and-avoid. The probability of two aeroplanes being on a collision course is essentially a function of traffic density, and the risk of collision is proportional to the square of the traffic density. The ClassC airspace around Toronto/LesterB. Pearson International Airport naturally concentrates circumnavigating traffic around its periphery. The airspace above the arc between Milton, Ontario, and Caledon also concentrates traffic vertically. The combination of surface elevation of 1400feet, flight at or above 1000feetagl, and a ClassC floor of 2500feet results in all traffic being concentrated vertically at the single altitude of 2400feet. It is unavoidable that ClassC airspace results in concentration of circumnavigating traffic around its periphery and this has proven to be a factor statistically in one-half of the collisions that have taken place between non-associated aircraft. Risk of collision can be reduced by dispersing traffic laterally, such as building a VFRroute structure with lateral separation between opposite-direction traffic. Such a routing structure would have to be clearly depicted on the VFRterminal area (VTA) chart. However, this structure would not eliminate conflict between aircraft on intersecting tracks, as in this occurrence. Reduction to the risk of collision between aircraft on intersecting tracks requires that traffic be dispersed vertically. Having 2000feet of vertical airspace between terrain and the ClassC floor rather than 1000feet at the location of the collision would provide a vertical space of 1000feet rather than the 100-foot space that existed in this case, reducing the likelihood of a collision. The risk could be reduced further by publishing routes and, where applicable, specific altitudes, in a form that is readily available to VFRpilots. Measures such as improving aircraft conspicuity, pilot scanning technique, and pilot traffic awareness can reduce risk, but they do not overcome the underlying physiological limitations that create the residual risk associated with unalerted see-and-avoid. There is only limited potential to further reduce risk by fine-tuning the unalerted see-and-avoid concept, and such an approach does little to address the risk of collision between VFRlight aircraft and IFR commercial traffic in congested areas. A meaningful improvement to the ability to see-and-avoid between uncontrolled VFR aircraft requires a practicable, affordable method of alerting pilots to the proximity of conflicting traffic. Reduction of conflicts between VFR aircraft and IFR traffic depends on making aircraft that are presently not transponder-equipped visible to ATC or to the IFRtraffic. Recent developments in Europe, specifically with respect to low-cost, low-power, lightweight LAST technology and collision-protection systems such as FLARM, which are compatible with ADS-B, indicate that technological solutions are emerging that can accomplish both of these objectives. These systems are not yet integrated into airworthiness and airspace standards or universally accepted by user communities. Taking into account the drawbacks of existing transponders due to cost, weight and power consumption, and the foreseeable evolution of ATMfrom a radar environment to ADS-B, these new systems offer a means to reduce the risk of mid-air collisions in the future provided that they are integrated into the Canadian regulatory, airworthiness, airspace and navigation framework and supported by general aviation.Analysis There was no indication that crew performance played a role in this accident or that either aeroplane was ill-equipped as to conspicuity devices or that those devices were not used appropriately. A realistic probability of either aeroplane detecting the other was 25percent, and without detection, the collision was unavoidable. The two aeroplanes were on a constant collision course; therefore, there was no relative angular movement that could be detected by peripheral vision to aid in detection. There was no other means of alerting either aeroplane as to the presence of the other. ATC does not provide traffic advisories in that airspace and TIS, which is capable of providing specific alerts and was carried by C-GCHN, depends on a ground radar service that is not available in Canada. The failure of the see-and-avoid principle to avert this collision reflects the residual risk that is inherent in sole reliance on unalerted see-and-avoid. The probability of two aeroplanes being on a collision course is essentially a function of traffic density, and the risk of collision is proportional to the square of the traffic density. The ClassC airspace around Toronto/LesterB. Pearson International Airport naturally concentrates circumnavigating traffic around its periphery. The airspace above the arc between Milton, Ontario, and Caledon also concentrates traffic vertically. The combination of surface elevation of 1400feet, flight at or above 1000feetagl, and a ClassC floor of 2500feet results in all traffic being concentrated vertically at the single altitude of 2400feet. It is unavoidable that ClassC airspace results in concentration of circumnavigating traffic around its periphery and this has proven to be a factor statistically in one-half of the collisions that have taken place between non-associated aircraft. Risk of collision can be reduced by dispersing traffic laterally, such as building a VFRroute structure with lateral separation between opposite-direction traffic. Such a routing structure would have to be clearly depicted on the VFRterminal area (VTA) chart. However, this structure would not eliminate conflict between aircraft on intersecting tracks, as in this occurrence. Reduction to the risk of collision between aircraft on intersecting tracks requires that traffic be dispersed vertically. Having 2000feet of vertical airspace between terrain and the ClassC floor rather than 1000feet at the location of the collision would provide a vertical space of 1000feet rather than the 100-foot space that existed in this case, reducing the likelihood of a collision. The risk could be reduced further by publishing routes and, where applicable, specific altitudes, in a form that is readily available to VFRpilots. Measures such as improving aircraft conspicuity, pilot scanning technique, and pilot traffic awareness can reduce risk, but they do not overcome the underlying physiological limitations that create the residual risk associated with unalerted see-and-avoid. There is only limited potential to further reduce risk by fine-tuning the unalerted see-and-avoid concept, and such an approach does little to address the risk of collision between VFRlight aircraft and IFR commercial traffic in congested areas. A meaningful improvement to the ability to see-and-avoid between uncontrolled VFR aircraft requires a practicable, affordable method of alerting pilots to the proximity of conflicting traffic. Reduction of conflicts between VFR aircraft and IFR traffic depends on making aircraft that are presently not transponder-equipped visible to ATC or to the IFRtraffic. Recent developments in Europe, specifically with respect to low-cost, low-power, lightweight LAST technology and collision-protection systems such as FLARM, which are compatible with ADS-B, indicate that technological solutions are emerging that can accomplish both of these objectives. These systems are not yet integrated into airworthiness and airspace standards or universally accepted by user communities. Taking into account the drawbacks of existing transponders due to cost, weight and power consumption, and the foreseeable evolution of ATMfrom a radar environment to ADS-B, these new systems offer a means to reduce the risk of mid-air collisions in the future provided that they are integrated into the Canadian regulatory, airworthiness, airspace and navigation framework and supported by general aviation. Toronto airspace design provides only limited vertical space beneath ClassC airspace northwest of Toronto. Consequently, both aeroplanes were at the same altitude when their tracks intersected, and they collided. There are inherent limitations and residual risk associated with the see-and-avoid principle; as a result, neither aeroplane saw the other in time to avert a mid-air collision.Findings as to Causes and Contributing Factors Toronto airspace design provides only limited vertical space beneath ClassC airspace northwest of Toronto. Consequently, both aeroplanes were at the same altitude when their tracks intersected, and they collided. There are inherent limitations and residual risk associated with the see-and-avoid principle; as a result, neither aeroplane saw the other in time to avert a mid-air collision. There is a high residual risk of failure inherently associated with the unalerted see-and-avoid principle as the sole defence against mid-air collision in congested airspace.Finding as to Risk There is a high residual risk of failure inherently associated with the unalerted see-and-avoid principle as the sole defence against mid-air collision in congested airspace. A technological means of alerting pilots to potential conflicts would augment the current see-and-avoid approach to averting mid-air collisions. Canadian air traffic control radars do not support traffic information service (TIS); therefore, aircraft equipped with TIS cannot obtain traffic advisory information. Light aircraft in Canada are not required to carry traffic alert and collision-avoidance system (TCAS) or any other form of traffic alerting system. As a result of technological advances, practicable light aircraft/glider collision warning devices and secondary surveillance radar (SSR) transponders are being developed. There has been little progress in implementing recommendations made by a safety review of visual flight rules operations in Toronto airspace following a previous mid-air collision.Other Findings A technological means of alerting pilots to potential conflicts would augment the current see-and-avoid approach to averting mid-air collisions. Canadian air traffic control radars do not support traffic information service (TIS); therefore, aircraft equipped with TIS cannot obtain traffic advisory information. Light aircraft in Canada are not required to carry traffic alert and collision-avoidance system (TCAS) or any other form of traffic alerting system. As a result of technological advances, practicable light aircraft/glider collision warning devices and secondary surveillance radar (SSR) transponders are being developed. There has been little progress in implementing recommendations made by a safety review of visual flight rules operations in Toronto airspace following a previous mid-air collision. Safety Action Action Taken NAV CANADA NAV CANADA has taken the following actions since this accident, some of which are within the framework of a level of service review of the Montral-Toronto-Windsor airspace corridor: In addition to the Claremont training area depictions, the latest Toronto area visual flight rules (VFR) charts (June 2007) have additional symbols depicting current parachute, ultralight, and flight training areas. The Toronto VFR terminal area (VTA) chart (July2007) contains a new depiction to illustrate the final approach areas for the instrument flight rules (IFR) approaches serving Hamilton with a cautionary note that pilots should be particularly vigilant in those areas for IFRaircraft on approach. The next cycle of the Canada Flight Supplement (CFS) will contain a number of these enhancements as well. On 05 July 2007, the ClassE airspace above 6500feet within 65nm of Toronto was designated as mandatory transponder airspace. Through 2006-2007, NAV CANADA, in conjunction with Transport Canada, has continued to provide briefing/information sessions to VFR pilots about operations in the Toronto area. Through the Airspace and Services reviews consultative workgroups, NAV CANADA continues to facilitate a dialogue on what types of VFR routes and information would best serve the VFR community, including discussion about the information contained on the back of United States VTA charts, common area frequencies, publication of VFR practice areas and transition routes. A comprehensive flight planning webpage has been set up, including aerodrome diagrams and other flight planning products, ensuring that pilots have free access to comprehensive and up-to-date aeronautical data. An Airspace and Services review has been initiated in the Montral-Toronto-Windsor corridor. Brampton Flying Club The Brampton Flying Club has taken the following safety actions: A pulse light system has been installed in all nine Cessna172s and one Piper Seminole of the Brampton Flying Club fleet to enhance visibility to other aircraft. The remainder of the fleet will also be fitted with pulse lights. The Brampton Flying Club has met with NAV CANADA and requested a modest raising of the floor of ClassC airspace to the north and west of the Brampton Airport and that the practice area be identified in a manner similar to the Claremont training area on the Toronto VTA and VFR navigation charts (VNC) and in the CFS. Action Required Vertical Structure of Airspace Research has shown that the probability of two aircraft being on a collision course is essentially a function of traffic density, and the risk of collision is proportional to the square of this density. Measures such as improving aircraft conspicuity, pilot scanning technique, and pilot traffic awareness can reduce risk, but they do not overcome the underlying physiological limitations that create the residual risk associated with unalerted see-and-avoid. The current design of Toronto airspace in the vicinity where this accident occurred results in a concentration of traffic in a very small altitude band, immediately below the floor of ClassC airspace, and immediately outside the radius at which the floor of ClassC airspace steps down toward the Toronto/LesterB. Pearson International Airport. The combination of a ground elevation of 1400feet above sea level (asl), flight at or above 1000feet above ground level (agl), and a ClassC floor of 2500feetasl results in all traffic being concentrated vertically at the single altitude of 2400feetasl. Changing the vertical structure of the airspace is one way of reducing this traffic concentration. Radar data reviewed for this area during a 10-day period around the accident indicated a heavy volume of VFR traffic below the ClassC floor, and several occasions where aircraft were within about 1500feet horizontally and 200feet vertically of each other. In this and other congested airspaces, it has been shown that the see-and-avoid principle for VFRaircraft is not always sufficient to ensure the safety of flight. Therefore, there continues to be a high risk of a mid-air collision between aircraft operating under the VFRprinciple in that airspace. Therefore, the Board recommends that: The Department of Transport, in coordination with NAV CANADA, take steps to substantially reduce the risk of collision between visual flight rules aircraft operating in ClassE airspace surrounding the Toronto/LesterB. Pearson International Airport. A08-03 Assessment Rating: Satisfactory in Part Safety Concern Collision-Protection Systems At the present time, a large number of VFR-only aircraft are not equipped with ModeC transponders, devices that can alert pilots of other aircraft in their vicinity. Furthermore, the lack of other, available, and installed technological methods of alerting VFR pilots to the presence of other aircraft increases the risk of a mid-air collision, especially in congested airspace. A meaningful improvement to the ability to see-and-avoid other VFR aircraft requires a practicable, affordable method of alerting pilots to the proximity of conflicting traffic. Recent developments in Europe, specifically with respect to low-cost, low-power, lightweight Light Aviation SSR [secondary surveillance radar] Transponder (LAST) technology and collision-protection systems such as FLARM that are compatible with automatic dependent surveillance broadcast (ADS-B), indicate that technological solutions are emerging that can accomplish both of these objectives. These new systems offer a means to reduce the risk of future mid-air collisions, provided they are integrated into the Canadian regulatory, airworthiness, airspace and navigation framework, and supported by general aviation. Aircraft operating under VFR in congested airspace using solely the see-and-avoid principle as a means of avoiding one another run an increased risk of collision, as this and other mid-air accidents have demonstrated. This single point of defence has shown that it is not sufficient to ensure safety; however, the Board believes that emerging technology that may be an affordable option to reduce this risk merits a serious look. The Board is concerned that, until technological solutions such as on-board collision-protection systems are mandated, a significant risk of collision between VFR aircraft will continue to exist in congested, high-density airspace areas in Canada. The Board notes that the risk of collision will increase as this traffic continues to grow, and see-and-avoid remains the primary means of defence. In addition, the Board recognizes that technological innovation is creating potential solutions that are both viable and economical. The Board appreciates that Transport Canada must examine all potential solutions before it can decide how best to recommend or mandate the adoption of one or more systems. On this basis, the Board requests that Transport Canada take a lead role, in cooperation with industry, in examining technological solutions, with the eventual aim of broad-scale adoption.